In this proposal we test the role of oxidative stress in the pathophysiology of preeclampsia. Oxidative stress, an imbalance of prooxidants and antioxidants, generates free radicals that injure tissues, especially vascular endothelium. Risk factors for preeclampsia and cardiovascular disease (e.g. obesity and insulin resistance) lead to cardiovascular morbidity by inducing oxidative stress. Lipid free radicals, especially as components of oxidized LDL (ox-LDL), alter endothelial cell structure and function. Data from our lab and others support alterations of endothelial cell function as a component of the pathophysiology of preeclampsia. In addition, preliminary data from our group indicates potential generation of pro oxidants by the preeclamptic placenta. We demonstrated increased xanthine oxidase/dehydrogenase, an enzyme which can generate superoxide, in invasive cytotrophoblast from preeclamptic women. Dr. Conrad determined increased circulating TNFa, which can generate free radicals, in preeclamptics. Dr. Fisher found that hypoxic placental tissue can generate TNFa in vitro. The potential role for oxidative stress is supported by excess lipid peroxides and antibodies against ox-LDL in preeclamptic women. We recently demonstrated material in the blood or plasma of preeclamptic women that increases ascorbate oxidation in vitro. We propose to characterize this activity. Whether these findings indicate cause or effect or are an epiphenomenon cannot be answered by available data. We propose definitively testing a causal role. We will use a nested case control study to study circulating markers of oxidative stress before, during and after preeclampsia. This tests whether changes are part of the unique pathophysiology of preeclampsia (antedate the syndrome and disappear after resolution), are a genetic predisposition (present before, during and after), or are secondary to other pathology (present only with overt disease). We will use the same design to determine the genesis of oxidative stress in individual patients which we propose results from the interaction of increased sensitive substrate (e.g. elevated triglycerides), and/or increased pro-oxidant (e.g. abnormalities of iron metabolism and elevated TNFa), and/or reduced antioxidant. We will test for tissue changes consistent with injury secondary to oxidative stress in vivo. We posit that the convergence at oxidative stress with subsequent endothelial cell dysfunction could explain the diverse risk factors and acute and long range maternal and neonatal morbidity of preeclampsia. Clearly establishing the role of oxidative stress in preeclampsia would justify clinical trials of appropriate antioxidants (as determined in these studies for the prophylaxis of preeclampsia.